How to obtain the data

At a facility’s internal level one important means of ensuring the efficient assessment of exposure situations is to create a complete information system that enables the collection, analysis and storage of data. As mentioned above, these data are not limited to dosimetric data but are also related, among other factors, to a job’s performance and the prevalent work conditions.

FIG. 2. Analysis of jobs.

Job description

Exposure conditions

Evaluation of the dose rates, surface contamination and aerosol activity

Working conditions

Determination of the period of exposure, temperature, place, lighting and special support

Staff and equipment

Identification of the necessary tools and equipment, specialists and workers

Co-ordination

Identification of other jobs that may influence the work conditions and radiation field at the workplace

Job analysis

Individual dose constraints;

collective dose targets

Knowledge from similar jobs in the past and well managed practices

Dose reduction measures

Identification of the possible improvement in equipment, tools, protective clothing and devices, shielding and measures for the reduction of the spread of the contamination

Work planning

Determination of the optimum period of exposure, number of workers, time schedule and work organization

Doses

Assessment of the expected individual dose distribution and collective dose

Preparation of feedback

Identification of the parameters necessary to follow in job performance for the purposes of post-job reviews or feedback

The data can be collected directly, either before, during and after jobs are carried out. In some cases the most efficient way to obtain data is to use systematically completed records, completed either by the radiation protection staff or by the job foremen both during and at the end of the work. These records need not be complex: simple record cards may suffice in many cases. In collecting data for repetitive jobs a coherence between the successive collection of data is important for an accurate analysis. In complex exposure situations (i.e. those that involve several sources or several types of job), computer based collection systems, most easily associated with an electronic operational dosimetry system, can be helpful in collecting information.

In some cases, such as at the design stage of a facility or for a new job or when no information is available, it may be necessary to use specific software to facilitate the following:

— Assessments of dose rates and their possible evolution in time;

— Simulations of the planned jobs in their environment;

— Combinations of data from all the planned jobs (for ambient dose rates, the length of time of exposure and the number of workers exposed) at the facility concerned, in order to obtain more generic indicators.

Periodic internal reviews or audits are also useful for evaluations, in particular reviews that concern an assessment of the awareness of workers and other types of human or organizational factors that lead to a poor performance. To obtain a more objective evaluation it can also be useful to ask for an external audit, which can be accomplished, for example, through alternate peer reviews in which two facilities participate in evaluations of one another.

The use of national databases can often be helpful if there is no job related information available to provide an indication of good practice or to identify areas for attention (see the example in Section 3.3.1.1).

3.3.1.1. Example 7: IAEA Regulatory Authority Information System

To support the regulatory authorities in its Member States the IAEA has developed the Regulatory Authority Information System (RAIS), which is being introduced in about 70 countries that receive IAEA assistance. The RAIS system consists of five modules, one of which covers individual dose monitoring. This module provides the regulatory authority with the necessary information on occupational exposure for its monitoring of safe operation. RAIS also provides comparisons with reference levels, such as investigation levels, and with dose constraints and dose limits, and reports on doses that exceed the reference levels.

3.3.2. International level

For some types of exposure situations there exist international databases that group dosimetric information by the types of radiation jobs performed in various facilities.

International data relevant to all types of work can been obtained through the periodically published reports of UNSCEAR on the sources and effects of ionizing radiation [21]. These reports include detailed data on occupational exposures in various sectors of industry and from various types of sources in different countries.

The main groups of occupational categories used in the report are nuclear fuel cycle, the medical uses of radiation, the industrial uses of radiation, the natural sources of radiation and defence related activities. Within each group distinctions are made between the major types of practices. For these practices the collected data concern, for each responding country, the number of monitored workers, the total annual collective effective dose, the average annual individual dose and the distribution of the number of workers and of the total collective dose per individual dose range. For nuclear power plants a more specific system has been developed (see the example in Section 3.3.2.1).

3.3.2.1. Example 8: Information System on Occupational Exposure

The field of occupational exposures at nuclear power plants has benefited since 1992 from an international programme called the Information System on Occupational Exposure (ISOE). This programme was launched by the OECD NEA to facilitate the exchange of experience in the management of occupational exposure among utilities and regulatory authorities from around the world. Since 1993 it has been co-sponsored by the IAEA to allow the participation of member countries not in the OECD NEA, and in 1997 the two agencies formed a joint ISOE secretariat.

The ISOE programme includes the management of an international database on occupational exposures and a network that allows the participants to obtain or exchange all types of information that relates to radiation protection in nuclear power plants. At the end of 2000 data from 92% of the world’s operating commercial nuclear reactors were included in the ISOE database.

The ISOE provides each member utility with the database, which contains detailed information on the individual and collective doses associated with the major activities performed in and outside refuelling outages, a description of the specific design features of the various reactor types and forms for the feedback of experience from some specific jobs performed by some utilities. An annual report contains an analysis of the data and a summary of the principal events in the participating countries that might have influenced the trends in occupational exposure [20].

4. MEANS OF REDUCING EXPOSURE

4.1. INTRODUCTION

Following the completion of an assessment it may be determined that there is a need to reduce doses and that there is a means by which the reduction can be carried out. The methods for reducing doses cover a broad spectrum, which ranges from simple organizational adjustments to a modification of the design of the facility concerned.

The ways in which exposure can be reduced are presented as singular factors (means) and may be applicable as singular factors. However, a combination of these factors (means) in many situations is likely to be more effective. This section begins with basic, yet essential, means and progresses towards more technical elements.

Not all of these means are necessarily applicable to all situations. There are many options for using them singly or in combination. The use of a combination of these means, and their relative order, should be delineated in an ALARA plan, which is discussed below. The decision of which means are applicable and should be adopted should precede the development of an action plan and is discussed in the next section.

Checklists are useful tools for carrying out the requirements of an optimization programme, and their uses are varied. Among other uses they can be used as an agenda for a job planning or post-job review meeting or can be distributed to workers to provoke thought for a process of information feedback. There are various types of checklist; the type used will likely vary depending upon the type and size of the facility concerned (see the examples in Annex II).

4.2. GLOBAL MEANS OF REDUCING EXPOSURE